The TV host is leading the event, being held at London's O2 Arena, as it aired live across the UK on ITV1 and ITVX.
However, Gilligan suffered a slip-up when introducing a performance by Capaldi, referring to him as "Sam Capaldi" by mistake – seemingly confused with another performer, Sam Smith, who performed later in the ceremony.
Following Capaldi's performance of Forget Me, which is up for single of the year, Gilligan apologised to the audience for the error.
Joking off the mistake, he said: "That goes to show how strong the drinks are at the Brit awards, they don't mess around!"
Viewers were quick to call out the mistake online, comparing it to awards night errors from years gone by.
"Mo Gilligan calling Lewis Capaldi Sam is giving John Travolta at the Oscars," wrote one.
"The irony of Lewis Capaldi singing Forget Me when Mo Gilligan has done exactly that," added a second.
A third noted: "Someone needs to take that glass of wine off Mo Gilligan sharpish. Sam Capaldi?!"
For the first time in Brit awards history, the ceremony was held on a Saturday rather than its typical midweek slot at London's O2 Arena.
Among the winners, Beyoncé was crowned international artist of the year, Harry Styles earned multiple gongs for pop/r&b artist and best artist, and Wet Leg took home the prize for best new artist.
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